I have been trying to visualise how a firing order for a 6 cylinder can be different from the 1-5-3-6-2-4 we are familiar with.
The Hall-Scott truck engine has the order 1-4-2-6-3-5. As I do'nt have an unassembled engine to play around with,my question is:
is this achieved by having the crank throws at different points to our familiar type,or does the crank throw remain the same,and camshaft open valves at different times.



This has had me puzzled for a while,and,as I said,without an engine to turn and puzzle over,I cannot visualise it.
Anyone understand the different timing systems?

regards,Rod

Hi Rod . . .

The crank layout and the cam must differ with this difference in firing order.

The Chevy crank has three pairs of throws 1-6, 2-5, and 3-4 which are at TDC together. Listed this way we can see that the firing order is simply odd-odd-odd, even-even-even, across the throw-pairs.

The H-S firing order implies a slightly different crank lay-out with throws paired the same but arranged in a different order in rotation 1-6, 3-4, 2-5 (the order in which they TDC). The cam has to follow the crank layout.

There is neat toy on this site dedicated to aircraft engines that shows firing order diagrams for different engines.

regards,
stock49

thanks for that stock49, your explanation makes sense.I do'nt suppose harmonics would play a big role in a slow revving engine like the Hall-Scott- or even if the HS sequence would make any difference to harmonics.

regards,Rod

Harmonics is the sound wave. It should look even on a graph or make a smooth feeling beat. It may have a different name at low rpm but...
One time a harmonic balancer fell off our car IN THE DRIVEWAY
even though the motor wasn't running fast it sounded awful. Like scary and klunky.
I think even a one cylinder motor like a lawn mower has some balance issues, otherwise they wouldn't put counter-weights on the crankshaft of a lawnmower engine.
Safety First Friends.

Greetings . . .

I don't see why the harmonics would all that different between these engines. I drew this up over coffee this morning:

Both designs are based on three sets of throws in planes 120 degrees apart. The difference is just the order in rotation.

I don't see why one design would be better/stronger then the other. They're just different variations on the same basic design. I don't think there's even any difference in the effort to cast or machine the pieces.

regards,
stock49

If you look closely at the firing order in the Hall-Scott engine and move the #1 to the rear and read it backwards, it comes out 1-5-3-6-2-4, so it's basically the same firing order with a different rotation, either of the crank or distributor, maybe both. Stock49 did a better job of explaining it than I did, but it's still your basic inline six cylinder firing order. I don't think that there is much you can do to change it and have the engine still function properly.

thanks for all your wisdom. I think I got it figured.

regards,Rod

I see, I didn't totally understand the question. I guess it is the same reasons GM distributors rotate clockwise and Fords rotate counter-clockwise.
Meanwhile, I gotta go build a better mousetrap, ha ha.